ModularEventMixin

ModularEventMixin lets a widget react to typed events tied to its own lifecycle. Register listeners in initState and the mixin cancels all of them automatically in dispose() — no manual cleanup.

Usage

Apply the mixin to a State and register listeners with on:

class CartBadge extends StatefulWidget {
  const CartBadge({super.key});
 
  @override
  State<CartBadge> createState() => _CartBadgeState();
}
 
class _CartBadgeState extends State<CartBadge> with ModularEventMixin {
  int _count = 0;
 
  @override
  void initState() {
    super.initState();
    on<ProductAdded>((event, context) {
      setState(() => _count++);
    });
  }
 
  @override
  Widget build(BuildContext context) => Text('$_count');
}

Fire events to it from anywhere:

ModularEvent.fire<ProductAdded>(ProductAdded(product));

Registering listeners

on<E>(
  void Function(E event, BuildContext? context) callback, {
  EventBus? eventBus,
  bool exclusive = false,
});

• context is mounted ? context : null — always null-check before using it.
• Registering on<E> twice for the same type replaces the previous listener.
• eventBus: omit to use the global defaultModularEventBus; pass a custom EventBus to isolate this widget’s listeners.
• exclusive: when true, uses a broadcast stream for the type.

Choosing an approach

Next steps

• Event Module
• Testing Events